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Spectral Properties of Substituted Coumarins in Solution and Polymer Matrices

机译：溶液和聚合物基质中取代香豆素的光谱性质

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The absorption and fluorescence spectra of substituted coumarins (2-oxo-2H-chromenes) were investigated in solvents and in polymer matrices. The substitutions involved were: (1) by groups with varying electron donating ability such as CH3, OCH3 and N(CH3)2, mainly, but not exclusively, in positions 7 and (2), by either CHO or 4-PhNHCONHN=CH- in position 3. While the spectra of non-substituted coumarin-3-carbaldehyde has absorptions at approximately 305 and 350 nm, substitution at position 7 leads to remarkable changes in the shape of the absorption spectrum and shifts the absorption to a longer wavelength. Similarly, the replacement of the formyl group with a semicarbazide group substantially influences the shape of the absorption spectrum, and coumarins which have only N(CH3)2 in position 7 experience small changes. These changes are associated with the increasing intramolecular charge transfer (ICT) character and increasing conjugation length of the chromophoric system, respectively, in the studied molecules. The fluorescence is almost negligible for derivatives which have H in this position. With increasing electron donating ability, and the possibility of a positive mesomeric (+M) effect of the substituent in position 7 of the coumarin moiety, the fluorescence increases, and this increase is most intense when N(CH3)2 substitutes in this position, for both 3-substituted derivatives. Spectral measurements of the studied coumarins in polymer matrices revealed that the absorption and fluorescence maxima lay within the maxima for solvents, and that coumarins yield more intense fluorescence in polymer matrices than when they are in solution. The quantum yield of derivatives which have a dimethylamino group in position 7 in polymer matrices approaches 1, and the fluorescence lifetime is within the range of 0.5–4 ns. The high quantum yield of 7-dimethylamino derivatives qualifies them as laser dyes which have kF higher than knr in the given medium. This is caused by stiffening of the coumarin structure in polar polymer matrices, such as PMMA and PVC, due to higher micro-viscosity than in solution and intermolecular dipole-dipole interaction between chromophore (dopant) and matrix.
机译：在溶剂和聚合物基质中研究了取代的香豆素（2-氧代-2H-色烯）的吸收和荧光光谱。所涉及的取代为：（1）主要通过但不限于在第7和（2）位上通过但不限于给电子能力不同的基团（例如CH3，OCH3和N（CH3）2）通过CHO或4-PhNHCONHN = CH -在位置3。未取代的香豆素3-甲醛的光谱在大约305和350 nm处有吸收，而在位置7的取代导致吸收光谱的形状发生显着变化，并将吸收移至更长的波长。类似地，用氨基脲基团取代甲酰基基团实质上影响吸收光谱的形状，并且在7位仅具有N（CH 3）2的香豆素经历小的变化。这些变化分别与所研究分子中分子内电荷转移（ICT）特性的增加和发色系统的共轭长度的增加有关。对于在该位置具有H的衍生物，荧光几乎可以忽略不计。随着电子给体能力的提高，以及香豆素部分7位上的取代基具有正的介晶（+ M）效应的可能性，荧光增强，当N（CH3）2取代该位置时，这种增强最为明显，对于两个3-取代的衍生物。对所研究的聚合物基质中的香豆素的光谱测​​量表明，吸收和荧光最大值位于溶剂的最大值之内，并且与在溶液中时相比，香豆素在聚合物基质中产生的荧光强度更高。在聚合物基质中第7位具有二甲氨基的衍生物的量子产率接近1，荧光寿命在0.5–4 ns范围内。 7-二甲基氨基衍生物的高量子产率使它们有资格用作给定介质中kF高于knr的激光染料。这是由于极性聚合物基质（例如PMMA和PVC）中的香豆素结构变硬而引起的，这是由于微粘度比溶液中的高，以及生色团（掺杂剂）和基质之间的分子间偶极-偶极相互作用。

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